The . The blood could be coming from any of several sources. A woman who sees blood after a bowel movement may actually be having vaginal bleeding. If the blood is really coming from the gastrointestinal tract, it can be due to hemorrhoids, infection or inflammation of the colon, or a blood clotting abnormality. In addition to those benign conditions, blood in the stoll can also indicate the presence of a tumor.
Your wife should see her doctor and have a colonoscopy. In the meanwhile, she should avoid anything that thins the blood (like aspirin). If she is on blood thinners like Plavix or coumadin, (warfarin) their dosages may need to change, but this should be done by her doctor--she should not stop taking them on her own.